求距离今天N天前的日期

function databox_request(startDataTime, endDataTime,n) {
    var dataTime = new Date(); //获取当前系统时间
    var date = dataTime.getDate();
    var fullYear = dataTime.getFullYear();
    var month = dataTime.getMonth() + 1;
    if (month < 10) {
        month = '0' + month;
    }
    if (date < 10) {
        date = '0' + date;
    }
    var endDate = fullYear + '-' + month + '-' + date;

    var dateStartTime = new Date(dataTime.getTime() - n * 24 * 3600 * 1000);//获取n天前日期
    var dateStart = dateStartTime.getDate();
    var fullYearStart = dateStartTime.getFullYear();
    var monthStart = dateStartTime.getMonth() + 1;
    if (monthStart < 10) {
        monthStart = '0' + monthStart;
    }
    if (dateStart < 10) {
        dateStart = '0' + dateStart;
    }
    var startDate = fullYearStart + '-' + monthStart + '-' + dateStart;
    startDataTime.datebox('setValue', startDate); //设置日期输入框的值
    endDataTime.datebox('setValue', endDate); //设置日期输入框的值
}